Read errno only once where possible

(cherry picked from commit e54e3af)

Author: eregon

src/main/ruby/truffleruby/core/errno.rb

@@ -48,6 +48,12 @@ def self.handle(additional = nil)
     raise SystemCallError.new(additional, err)
   end
 
+  def self.handle_errno(errno)
+    return if errno == 0
+
+    raise SystemCallError.new(nil, errno)
+  end
+
   def self.errno
     Truffle::POSIX.errno_address.read_int
   end

src/main/ruby/truffleruby/core/io.rb

@@ -2306,7 +2306,7 @@ def sysread(number_of_bytes, buffer=undefined)
     raise IOError unless @ibuffer.empty?
 
     str, errno = Truffle::POSIX.read_string(self, number_of_bytes)
-    Errno.handle unless errno == 0
+    Errno.handle_errno(errno) unless errno == 0
 
     raise EOFError if Primitive.nil? str
 

src/main/ruby/truffleruby/core/posix.rb

@@ -353,7 +353,7 @@ def self.read_string_at_least_one_byte(io, count)
       if TRY_AGAIN_ERRNOS.include? errno
         IO.select([io])
       else
-        Errno.handle
+        Errno.handle_errno(errno)
       end
     end
   end
@@ -368,7 +368,7 @@ def self.read_string_nonblock(io, count)
     elsif TRY_AGAIN_ERRNOS.include? errno
       raise IO::EAGAINWaitReadable
     else
-      Errno.handle
+      Errno.handle_errno(errno)
     end
   end
 
@@ -432,7 +432,7 @@ def self.write_string_native(io, string, continue_on_eagain)
               return written
             end
           else
-            Errno.handle
+            Errno.handle_errno(errno)
           end
         end
         written += ret
@@ -474,7 +474,7 @@ def self.write_string_nonblock_native(io, string)
         if TRY_AGAIN_ERRNOS.include? errno
           raise IO::EAGAINWaitWritable
         else
-          Errno.handle
+          Errno.handle_errno(errno)
         end
       end
       written

src/main/ruby/truffleruby/core/process.rb

@@ -122,14 +122,14 @@ def self.clock_getres(id, unit=:float_second)
             raise Errno::EINVAL
           else
             res_for_id = Truffle::POSIX.truffleposix_clock_getres(id)
-            if res_for_id == 0 then
+            if res_for_id == 0
               Errno.handle
             else
               res_for_id
             end
           end
 
-    if :hertz == unit then
+    if :hertz == unit
       1.0 / nanoseconds_to_unit(res,:float_second)
     else
       nanoseconds_to_unit(res,unit)

src/main/ruby/truffleruby/core/truffle/io_operations.rb

@@ -152,27 +152,29 @@ def self.select(readables, readable_ios, writables, writable_ios, errorables, er
                                                remaining_timeout)
           end
 
-          result = if primitive_result < 0
-                     if Errno.errno == Errno::EINTR::Errno
-                       if timeout
-                         # Update timeout
-                         now = Process.clock_gettime(Process::CLOCK_MONOTONIC, :microsecond)
-                         waited = now - start
-                         if waited >= timeout
-                           nil # timeout
-                         else
-                           remaining_timeout = timeout - waited
-                           :retry
-                         end
-                       else
-                         :retry
-                       end
-                     else
-                       Errno.handle
-                     end
-                   else
-                     primitive_result
-                   end
+          result =
+            if primitive_result < 0
+              errno = Errno.errno
+              if errno == Errno::EINTR::Errno
+                if timeout
+                  # Update timeout
+                  now = Process.clock_gettime(Process::CLOCK_MONOTONIC, :microsecond)
+                  waited = now - start
+                  if waited >= timeout
+                    nil # timeout
+                  else
+                    remaining_timeout = timeout - waited
+                    :retry
+                  end
+                else
+                  :retry
+                end
+              else
+                Errno.handle_errno(errno)
+              end
+            else
+              primitive_result
+            end
         end while result == :retry
 
         if result == 0